Well over a decade ago the first diphtheria toxin-based fusion protein toxin, DAB389IL-2 (Ontak(R)) was in development as the first of a new class of receptor specific therapeutic agent. This fusion protein gained FDA approval five years ago for the treatment of refractory cutaneous T cell lymphoma. The fusion protein toxin technology has not been widely developed due adverse events, especially vascular leak syndrome (VLS), associated with administration of these agents. The Anjin Group Inc [AGI] proposes to develop a third generation diphtheria toxin-based platform, modified to reduce VLS. Fusion protein toxins developed from such a toxophore may have broader clinical application due to an altered risk benefit profile for patients including those with non-life threatening disease.